The troubles of being the SO of a single mother

I have to admit I am having troubles being a "dad" to three boys I've not raised. Some of the things these children take for granted astound me.

Anyone else out there who reads my journal have any experience being a defacto stepparent and willing to give me advice?

I'm trying hard to keep my distance with some of the issues I have. I realize that their father and I have extremely opposing views on certain things (which is why the boys have some of their misconceptions) and I realize that their father is always going to be their father ... and I'm NOT trying to replace him.

Just venting really ... I'd rather blow off steam here than in a nonconstructive way.